Several different solutions are previously there known for indicating to a user of an apparatus that a key has been pressed long and hard enough to enable the keystroke to be registered.
A previously known solution is to provide each key with a mechanism which produces a “click” that can be felt and/or heard by a user when the user presses a key. The problem with such prior art mechanical solutions is the space required by the mechanism. It is in practice necessary to design the key such that the key is allowed to move a predetermined distance before it reaches the location where the “click” is generated. The space required by the movement and the space required by the mechanism itself mean that the entire keypad turns out to be relatively thick.
Another previously known solution is to provide an apparatus with means for generating a sound signal each time a keystroke is registered. Such a solution has typically been used in connection with thin membrane keypads since this solution does not increase the thickness of the keypad because the means necessary for generating the sound can be located somewhere else in the apparatus. The problem with this prior art solution is, however, that the “beep” generated in connection with each keystroke is rather annoying, and most users would thus prefer to turn off such a “beep”. This, however, is not possible in practice because then the user will not know when a keystroke has been registered, since this solution does not give any tactile feedback to the user. Thus the user might, by mistake, press the same key several times although the intention was only to press once.